Yes, Bring Your Own Food. Particularly when traveling. No, just all time. And definitely if you are someone who gets cranky/insane when overly hungry. Just have healthy snacks around. Pack them in pockets and nooks in bags. There is no downside to this.
Jane's Lessons Learned 
I can really relate to this. This week I have been packing an apple, some nuts and a cheese stick and it has REALLY helped me with sugar lows, saving time and money. The best part is I feel better.
Downside: Sometimes mice eat them. Seriously.